Note: If you have more than one Haskell compiler on your system,
use the --with-compiler option for the
configure step. That will ensure that Cabal
uses the correct compiler during the entire installation process.
For example:

Without this, I didn't know that you need to use that
flag. I just ran runhaskell with an explicit path to the compiler
that I wanted. Cabal then ran the wrong ghc-pkg, and registered
the installation to the wrong compiler.

Question about DARCS: How does one install from a DARCS repository? In some places this seems to be a "natural thing to do" for some people but it isn't self explanatory.